Stardock, publisher of Sins of a Solar Empire and owner of distribution service Impulse, said it believes Impulse rests in second place after Valve's popular Steam in the digital distribution rankings in terms of market share by revenue.

"Our estimation is that Steam - as the current market leader - enjoys approximately 70 percent of the overall digital distribution market with Impulse at 10 percent and all others combined at 20 percent in terms of actual dollars generated per month," wrote Stardock chief Brad Wardell in the company's customer report for 2009 [PDF], released this week.

"Steam and Impulse both have the advantage of exclusive content (Left 4 Dead, Half-Life, Sins of a Solar Empire, Demigod, etc.)," he added. Impulse launched in 2008, while Valve launched Steam in 2003. Years prior to Impulse, Stardock was developing digital distribution initiatives including Stardock Central and TotalGaming.net. Digital competitors outside of Steam and Impulse include Direct2Drive and GamersGate, among others.

Wardell said he expects that digital distribution will make up around 25 percent of the revenues "for a typical PC game publisher on a new title" in calendar 2009.

Wardell said that Stardock is working to further evolve the Impulse service by improving the user experience, focusing on a better community experience and attracting increasing amounts of content for the online store.

The CEO noted a few key challenges for Impulse going forward. First, regional pricing has proved to be a hurdle, as Stardock needs to sign separate agreements with multiple overseas arms of large game publishers instead of one straightforward contract. "Thus far, our competitors have a significant head-start in this area," he said.

Wardell also said, "Another trend we have seen in the past year has been Valve’s successful work with getting Steamworks licensed as a DRM solution by major publishers. Once a game requires Steamworks, it is effectively cut off from us, which limits our content. Examples of this include THQ’s Dawn of War II, Sega’s Empire: Total War, and more recently Activision’s Call of Duty 4: Modern Warfare 2."

"The problem is that it is not practical for us to install a game that in turn requires the installation of a competitor’s store and platform in order to play it," Wardell said. This sentiment is reflected in Stardock's decision not to carry Modern Warfare 2 on Impulse.

Wardell also said that getting content up fast enough "has been an ongoing challenge." He explained, "Not only must updates be put up quickly but users expect tremendous download speeds no matter where they are located." Improvements, Wardell said, will come with Impulse Phase 5.